TW202309623A - Polarizing plate and image display device - Google Patents

Abstract

The present invention provides a polarizing plate capable of inhibiting transmittance from a decrease in a high temperature environment. The polarizing plate has a polarizing element in which a dichroic dye is absorbed and oriented on a polyvinyl alcohol-based resin, and a transparent protective film laminated on at least one surface of the polarizing element. The polarizing element and the transparent protective film are bonded together by an adhesive layer formed from an adhesive containing a first compound and a second compound, wherein the first compound is a compound having a nitroxyl radical or a nitroxide group, and the second compound is a cyclodextrin.

Description

Polarizing plate and image display device

The invention relates to a polarizing plate and an image display device.

Liquid crystal display devices are widely used not only in liquid crystal televisions but also in personal computers, mobile devices such as mobile phones, and automobiles such as navigators. Generally, a liquid crystal display device includes a liquid crystal panel in which a polarizing plate is attached to both sides of a liquid crystal cell with an adhesive (pressure-sensitive adhesive, also known as a pressure-sensitive adhesive), and displays are controlled by the light from the backlight through the liquid crystal panel. In recent years, like liquid crystal display devices, organic EL (electroluminescent) display devices have been widely used in televisions, mobile devices such as mobile phones, and automotive applications such as navigators. In an organic EL display device, in order to prevent external light from being reflected by the metal electrode (cathode) and being recognized as a mirror surface, a circular polarizing plate (including a polarizing element and a λ/4 plate) is sometimes arranged on the identification side surface of the image display panel. layered body).

As described above, polarizing plates are more likely to be mounted on automobiles as components of image display devices such as liquid crystal display devices and organic EL display devices. Compared with mobile applications such as TVs and mobile phones, polarizers used in image display devices for automobiles are more exposed to high-temperature environments, and require small changes in characteristics at higher temperatures (high-temperature durability).

On the other hand, for the purpose of preventing the damage of the image display panel due to impact from the outer surface, etc., a front transparent plate (also called a transparent resin plate, a glass plate, etc.) is provided on the side of the image display panel that is closer to the recognition side The composition of "window layer") is increased. In an image display device including a touch panel, a configuration in which the touch panel is provided on the viewing side of the image display panel and the front transparent plate is provided on the viewing side of the touch panel is widely used.

In such a configuration, when there is an air layer between the image display panel and transparent members such as the front transparent plate and the touch panel, external light reflection occurs at the interface of the air layer due to light reflection, and the visibility of the screen may decrease. tendency. Therefore, the configuration of filling the space between the polarizing plate and the transparent member disposed on the viewing side surface of the image display panel with a layer other than the air layer, usually a solid layer (hereinafter referred to as "interlayer filler") has begun to be widely used. use. The interlayer filler is preferably a material having a refractive index close to that of the polarizing plate or the transparent member. As an interlayer filler, an adhesive or a UV-curable adhesive is used for the purpose of suppressing a decrease in visibility due to reflection at an interface and then fixing between members (see, for example, Patent Document 1).

The structure filled with the above-mentioned interlayer filler is widely used in mobile applications such as mobile phones, which are often used outdoors. In addition, due to the increasing demand for visibility in recent years, even for automotive applications such as navigation devices, a front transparent plate is placed on the surface of the image display panel, and the space between the panel and the front transparent plate is filled with a solid layer such as an adhesive layer. The use of composition is also under review.

However, in the case of adopting such a configuration, it has been reported that the transmittance of the polarizing plate is greatly reduced in a high-temperature environment. In Patent Document 2, as a solution to this problem, it is proposed that by setting the water content per unit area of the polarizing plate to be below a predetermined amount and setting the saturated water absorption of a transparent protective film adjacent to the polarizing element to be below a predetermined amount, A method of suppressing a decrease in penetration rate.

[Prior Art Literature]

[Patent Document]

[Patent Document 1] Japanese Laid-Open Patent Publication No. H11-174417

[Patent Document 2] Japanese Laid-Open Patent Publication No. 2014-102353

However, even such a polarizing plate cannot sufficiently suppress a decrease in transmittance in a high-temperature environment.

An object of the present invention is to provide a polarizing plate capable of suppressing a decrease in transmittance even when exposed to a high-temperature environment, and an image display device using the polarizing plate.

The present invention provides the following polarizing plate and image display device.

[1] A polarizing plate comprising a polarizing element in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element;

Wherein, the above-mentioned polarizing element and the above-mentioned transparent protective film are bonded by an adhesive layer formed by an adhesive containing the first compound and the second compound;

The aforementioned first compound is a compound having a nitroxyl radical or a nitrogen oxide group;

The aforementioned second compound is cyclodextrin (cyclodextrin).

[2] The polarizing plate according to [1], wherein the first compound is an N-oxyl compound.

[3] The polarizing plate according to [1] or [2], wherein the second compound is at least one selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin .

[4] The polarizing plate according to any one of [1] to [3], wherein the adhesive contains a polyvinyl alcohol-based resin.

[5] The polarizing plate according to [4], wherein, in the adhesive, the content of the first compound is not less than 0.1 parts by mass and not more than 400 parts by mass relative to 100 parts by mass of the polyvinyl alcohol-based resin.

[6] The polarizing plate according to [4] or [5], wherein, in the adhesive, the content of the second compound is 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the polyvinyl alcohol-based resin. .

[7] The polarizing plate according to any one of [1] to [6], wherein the adhesive layer has a thickness of not less than 0.01 μm and not more than 7 μm.

[8] The polarizing plate according to any one of [1] to [7], wherein the polarizing plate is used in an image display device;

In the image display device, it is provided so that both surfaces of the polarizing plate are in contact with the solid layer.

[9] An image display device comprising: an image display unit; a first adhesive layer laminated on a viewing side surface of the image display unit; and a [ The polarizing plate according to any one of 1] to [8].

[10] The image display device according to [9], further comprising: a second adhesive layer laminated on the viewing side surface of the polarizing plate; and a transparent member laminated on the viewing side surface of the second adhesive layer.

[11] The image display device according to [10], wherein the transparent member is a glass plate or a transparent resin plate.

[12] The image display device according to [10], wherein the transparent member is a touch panel.

According to the present invention, it is possible to provide a polarizing plate that suppresses a decrease in transmittance even when exposed to a high-temperature environment when used in an image display device configured by interlayer filling in which both sides of the polarizing plate are in contact with solid layers. Furthermore, by using the polarizing plate of the present invention, it is possible to provide an image display device that suppresses a decrease in transmittance even when exposed to a high-temperature environment.

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments.

[polarizer]

The polarizing plate of this embodiment includes a polarizing element in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element. The polarizer and the transparent protective film are bonded by an adhesive layer formed of an adhesive containing the first compound and the second compound. The first compound is a compound having a nitroxide radical or a nitroxide group. The second compound is cyclodextrins.

As a conventional polarizing plate excellent in high-temperature durability, for example, a polarizing plate that suppresses a decrease in transmittance even after the polarizing plate is left alone in an environment at a temperature of 95° C. for 1000 hours is known. However, even such a polarizing plate is applied to double-sided contact of a polarizing plate in which one side of the polarizing plate is bonded to an image display unit, and the other side is bonded to a transparent member such as a touch panel or a front panel. In the case of an image display device with a solid layer structure (hereinafter referred to as "interlayer filling structure"), if it is left for 200 hours in an environment at a temperature of 95°C, it can be seen that the transmittance at the in-plane center of the polarizing plate is significantly reduced. . The transmittance of the polarizing plate in a high-temperature environment is obviously reduced, which is considered to be a problem that is particularly likely to be caused when an image display device composed of interlayer filling is exposed to a high-temperature environment.

In the image display device composed of interlayer filling, the polarizing plate whose transmittance is significantly reduced has 1100cm ^-1 near (from =CC=bond) and 1500cm ^-1 near (from-C=C-bond) due to Raman spectrometry. knot) peak, which is considered to form the polyene structure (-C=C) _n -. The polyolefin structure is presumed to be produced by dehydration of the polyvinyl alcohol-based resin constituting the polarizer (Patent Document 2, paragraph [0012]).

The polarizing plate according to this embodiment is incorporated into an image display device having an interlayer filling structure, and has excellent high-temperature durability that suppresses a decrease in transmittance even when exposed to a high-temperature environment at a temperature of 105° C., for example. Such an effect is obtained because the polarizing plate is provided with an adhesive layer containing the first compound and the second compound. It is presumed that this is because the synergistic effect of the first compound and the second compound suppresses polymerization of the polyvinyl alcohol-based resin constituting the polarizing element. caused by olefination. It was confirmed that such an effect is effective not only when the moisture content of the polarizing plate is low, but also when the moisture content of the polarizing plate is high.

The polarizing plate of this embodiment may have at least one of the following (a) and (b), for example.

(a) The moisture content of the polarizing element is not less than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and not more than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%.

(b) The moisture content of the polarizing plate is not less than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and not more than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%.

Regarding the feature of (a) or (b) above, even if the polarizing plate according to the present embodiment has the feature further defined in (a1) or (b1) below, it has the effect of improving high temperature durability.

(a1) The moisture content of the polarizing element exceeds the equilibrium moisture content of 45% or 50% relative humidity at a temperature of 20°C and is not more than an equilibrium moisture content of 80% or 70% of a relative humidity at a temperature of 20°C.

(b1) The moisture content of the polarizing plate exceeds the equilibrium moisture content of 45% or 50% relative humidity at a temperature of 20°C and is equal to or lower than the equilibrium moisture content of 80% or 70% of a relative humidity at a temperature of 20°C.

The method for manufacturing a polarizing plate in this embodiment may include a step of adjusting the moisture content so as to have at least one of the above-mentioned features (a) and (b), or may not include the step of adjusting the moisture content.

<Polarizer>

A known polarizer can be used as a polarizer in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol (hereinafter referred to as "PVA") resin layer. As a polarizing element, for example: a stretched film obtained by dyeing a PVA-based resin film as a PVA-based resin layer with a dichroic dye and uniaxially stretching it, or coating a substrate film containing a PVA-based resin. The coating solution is formed by forming a coating layer as a PVA-based resin layer on a base film to obtain a laminate, dyeing the coating layer with a dichroic dye, and uniaxially stretching the laminate film. Elongation may be performed after dyeing with a dichroic dye, may be performed while dyeing, or may be performed after elongation.

The PVA-based resin included in the PVA-based resin layer can be obtained by saponifying polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include copolymers of vinyl acetate and other monomers that may be copolymerized with the vinyl acetate, in addition to polyvinyl acetate that is a homopolymer of vinyl acetate. Examples of other monomers that can be copolymerized include unsaturated carboxylic acids, olefins such as ethylene, vinyl ethers, unsaturated sulfonic acids, and the like.

The degree of saponification of the PVA-based resin is preferably at least 85 mol%, more preferably at least 90 mol%, and still more preferably at least 99 mol% and not more than 100 mol%. The degree of polymerization of the PVA-based resin is, for example, from 1,000 to 10,000, preferably from 1,500 to 5,000. PVA-based resins may be modified, for example, aldehyde-modified polyvinyl formal, polyvinyl acetal, polyvinyl butyral, and the like.

Examples of the dichroic dye adsorbed and aligned to the polyvinyl alcohol-based resin layer include iodine or a dichroic dye. The dichroic pigment is preferably iodine. As dichroic dyes such as Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, GreenLG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue, Direct Fast Orange S, Fast Black, etc.

The thickness of the polarizing element is preferably from 3 μm to 35 μm, more preferably from 4 μm to 30 μm, still more preferably from 5 μm to 25 μm. With the thickness of the polarizing element being 35 μm or less, it is easy to suppress the effect of polyalkyleneization of PVA-based resins on the reduction of optical properties in a high-temperature environment, and it is easy to achieve the desired optical properties with the thickness of the polarizing element being 3 μm or more polarizer.

The polarizing element of the polarizing plate of this embodiment preferably contains the first compound and the second compound. Polarizing plate Since the polarizing element and the transparent protective film are bonded with an adhesive layer formed by an adhesive containing the first compound and the second compound, it is estimated that a part of the first compound and a part of the second compound that migrated from the adhesive layer include in polarizing elements. With such a polarizing element Since the polarizing plate of the component has an adhesive layer containing the first compound and the second compound, the transmittance is not easily lowered even if it is exposed to a high temperature environment. Furthermore, by providing the adhesive layer containing the first compound and the second compound, the polarization degree can be suppressed from decreasing even when the polarizing plate is exposed to a high-temperature environment. When the degree of polarization of the polarizing plate is lowered, light leakage (hereinafter referred to as “orthogonal leakage”) will easily occur when two polarizing plates are arranged in a crossed polarizing relationship. Even if the polarizing plate of this embodiment is exposed to Since the degree of polarization does not easily decrease under high-temperature environments, it becomes easy to suppress cross leakage. It is speculated that due to the synergistic effect of the first compound and the second compound contained in the polarizing element, the polyalkyleneization of the PVA-based resin is suppressed, thereby suppressing the decrease in the transmittance of the polarizing plate exposed to a high temperature environment, and also suppressing reduction in polarization.

As a method of making the polarizing element contain the first compound and the second compound, for example: a method of moving the first compound and the second compound from the adhesive layer to the polarizing element as described above; manufacturing a polarizing element containing the first compound and the second compound method; a combination of the two methods. For example, when manufacturing a polarizing element, one of the first compound and the second compound is contained in the polarizing element, and both the first compound and the second compound are contained in the adhesive layer constituting the polarizing plate.

As a method of manufacturing a polarizing element containing the first compound and the second compound when manufacturing a polarizing element, for example, a method of immersing a PVA-based resin layer in a processing solvent containing the first compound and/or the second compound, or adding the processing solvent to PVA It is a method of spraying, flowing or dripping the resin layer. Among them, the method of using a PVA-based resin layer and immersing it in a treatment solvent containing both the first compound and the second compound is preferable. Specific examples of the first compound and the second compound are, for example, contained in an adhesive agent described later.

The step of immersing the PVA-based resin layer in a treatment solvent containing the first compound and the second compound can be combined with swelling, stretching, crosslinking, and cleaning in the manufacturing method of the polarizing element described later. Steps such as washing are carried out at the same time, and may be provided separately from these steps. The step of adding the first compound and the second compound to the PVA-based resin layer is preferably performed after dyeing the PVA-based resin layer with iodine, and more preferably simultaneously with the crosslinking step after dyeing. According to such a method, the hue change is small, and the influence on the optical characteristics of the polarizing element can be reduced.

(1st compound)

The first compound is a compound having a nitroxide radical or a nitroxide group. From the point of view of relatively stable free radicals at room temperature and air, as the first compound, for example, N-oxyl compounds (compounds having C-N(-C)-O‧ as functional groups) (O‧represents oxygen free radicals) , bonded to N)), you can use learners. As an N-oxyl compound, the organic group compound etc. which have the following structures are mentioned, for example. Compounds having nitroxide radicals or nitroxide groups may be used alone or in combination of two or more.

[In the above formula (1), R ¹ represents an oxygen radical, R ² to R ⁵ independently represent a hydrogen atom or an alkyl group with 1 to 10 carbon atoms, and n represents 0 or 1. ]

In the above formula (1), the left side of the dotted line represents an arbitrary organic group or a hydrogen atom.

As a compound which has the said organic group, the compound etc. which are represented by following formula (2)-(5) are mentioned, for example.

[In the above formula (2), ^R1 to ^R5 and n represent the same meaning as above, ^R6 represents a hydrogen atom or an alkyl group, an acyl group or an aryl group with 1 to 10 carbon atoms, and n represents 0 or 1 . ]

[In the above formula (3), R ¹ to R ⁵ and n represent the same meaning as above, R ⁷ and R ⁸ independently represent a hydrogen atom or an alkyl, acyl or aryl group with 1 to 10 carbon atoms. ]

[In the above-mentioned formula (4), R ¹ to R ⁵ and n represent the same meaning as above, R ⁹ to R ¹¹ independently represent a hydrogen atom or an alkyl group, an acyl group, an amino group, an acyl group, an amino group, Alkoxy, hydroxy or aryl. ]

[In the above formula (5), ^R1 to ^R5 and n represent the same meaning as above, and ^R12 represents a hydrogen atom or an alkyl group, an acyl group, an amino group, an alkoxyl group, a hydroxyl group with 1 to 10 carbon atoms or aryl. ]

In the above formulas (1) to (5), R ² to R ⁵ are preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, from the viewpoint of ease of acquisition. In the above formula (2), R ⁶ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom, from the viewpoint of ease of acquisition. In the above formula (3), R ⁷ and R ⁸ are independently preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom, from the viewpoint of ease of acquisition. In the above formula (4), R ⁹ to R ¹¹ are independently preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms from the viewpoint of ease of acquisition. In the above formula (5), from the viewpoint of ease of acquisition, R ¹² is preferably a hydroxyl group, an amino group or an alkoxy group. In the above formulas (1) to (5), n is preferably 1 from the viewpoint of ease of acquisition.

Examples of N-oxyl compounds include those described in JP-A-2003-64022, JP-A-11-222462, JP-A-2002-284737, and WO2016/047655. As the N-oxyl compound, 4-hydroxy-2,2,6,6-tetramethyl-1-pyridine oxide is preferably used.

Examples of the first compound include the following compounds and the like.

[In the formula (6), R represents a hydrogen atom or an alkyl, acyl or aryl group having 1 to 10 carbon atoms. ]

The molecular weight of the first compound is preferably 1,000 or less, more preferably 500 or less, and still more preferably 300 or less, from the viewpoint of effectively trapping radicals generated in the polyalkylene reaction. The lower limit of the molecular weight is not particularly limited, and may be 80, for example.

(2nd compound)

The second compound is cyclodextrins. Cyclodextrin is a non-reducing cyclic oligosaccharide in which glucose is bonded by α-1,4 bonds to form a ring. The larger the number of glucose constituting cyclodextrins, the larger the inner diameter of the cavity in the molecule. As the cyclodextrins used as the second compound, it is preferable that the number of constituent glucose is 6 or more, for example, the number of constituent glucose is 6, 7, 8, 9 α, β, γ , δ-cyclodextrin. As cyclodextrins, in α, β, γ, δ-cyclodextrins, including branched sugar chains Branched cyclodextrin with oligosaccharides such as glucose and maltose. As cyclodextrins, the above-mentioned cyclodextrin or branched cyclodextrin further includes: an alkyl group bonded with a methyl group; 2-hydroxyethyl group, 2-hydroxypropyl group, 2,3-dihydroxypropyl group, Cyclodextrin derivatives of hydroxyalkyl groups such as 2-hydroxybutyl, etc. Cyclodextrins can be used alone or in combination of two or more.

(feature (a))

In the case where the polarizing plate has the above feature (a), the moisture content of the polarizing element is above the equilibrium moisture content at 20°C relative humidity of 30% and below the equilibrium moisture content at 20°C relative humidity of 80%. The moisture content of the polarizing element may exceed the equilibrium moisture content of 45% or 50% relative humidity at a temperature of 20°C and be below the equilibrium moisture content of 80% or 70% of a relative humidity at a temperature of 20°C. When the moisture content of the polarizing element is lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30%, the handling property of the polarizing element is low, and it becomes easy to break. When the moisture content of the polarizing element is higher than the equilibrium moisture content of 45% or 50% relative humidity at a temperature of 20°C, it is presumed that the polyalkyleneization of the PVA-based resin is likely to be promoted. The adhesive layer of the second compound can suppress the polyalkyleneization of PVA-based resin.

As a method of confirming that the moisture content of the polarizing element is within the range of not less than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and not more than an equilibrium moisture content at a temperature of 20° C. and a relative humidity of 80%, for example, adjust the temperature to the above-mentioned relative humidity. It is considered as a method to achieve equilibrium with the environment if the quality does not change for a certain period of time, or pre-calculate the equilibrium moisture content of the polarizing element adjusted to the above-mentioned temperature and the above-mentioned relative humidity range, by polarizing A method of confirming the moisture content of an element by comparing it with a precalculated equilibrium moisture content.

As a method of manufacturing a polarizing element with a moisture content above the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and below an equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%, there is no specific Not limited, for example, the method of storing the polarizing element for 10 minutes to 3 hours in an environment adjusted to the above temperature and the above relative humidity range, or the method of heat treatment at a temperature of 30°C to 90°C.

As another preferable method of manufacturing a polarizing element having a moisture content in the above-mentioned range, for example, a laminate in which a transparent protective film is laminated on at least one side of the polarizing element or a polarizing plate composed of a polarizing element is adjusted to the above-mentioned temperature and the above-mentioned relative temperature. The method of storing in the environment of the range of humidity for 10 minutes to 120 hours or the method of heat-treating at a temperature of 30°C to 90°C. Alternatively, when producing an image display device configured by interlayer filling, the image display panel in which the polarizer is laminated on the image display unit is stored in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity range for 10 minutes or more and 3 hours or less Or after heating at a temperature of 30° C. to 90° C., it is bonded to a transparent member such as a front panel.

(feature (b))

In the case where the polarizing plate has the above feature (b), the moisture content of the polarizing plate is above the equilibrium moisture content at 20°C relative humidity of 30% and below the equilibrium moisture content at 20°C relative humidity of 80%. The moisture content of the polarizing plate may exceed the equilibrium moisture content of 45% or 50% relative humidity at a temperature of 20°C and be below the equilibrium moisture content of 80% or 70% of a relative humidity at a temperature of 20°C. When the moisture content of the polarizing plate is lower than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30%, the handling property of the polarizing plate is low, and the polarizing plate is easily broken. When the moisture content of the polarizing plate exceeds the equilibrium moisture content of 45% or 50% relative humidity at a temperature of 20°C, it is presumed that the polyalkyleneization of the PVA-based resin is likely to be promoted. The adhesive layer of the second compound can suppress the polyalkyleneization of PVA-based resin.

As a method of confirming that the moisture content of the polarizing plate is within the range of not less than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and not more than an equilibrium moisture content at a temperature of 20° C. and a relative humidity of 80%, for example, the temperature and the above-mentioned relative humidity are adjusted to It is considered as a method to achieve equilibrium with the environment if the quality does not change for a certain period of time, or pre-calculate the equilibrium moisture content of the polarizing plate adjusted to the above-mentioned temperature and the above-mentioned relative humidity range, by polarizing The method of confirmation by comparing the moisture content of the board with the pre-calculated equilibrium moisture content.

There are no particular limitations on the method of producing a polarizing plate with a moisture content equal to or higher than the equilibrium moisture content at a temperature of 20°C and a relative humidity of 30% and not more than an equilibrium moisture content at a temperature of 20°C and a relative humidity of 80%. The method of storing the polarizing plate for 10 minutes to 3 hours in an environment within the range, or the method of heat treatment at a temperature of 30°C to 90°C. Or when producing an image display device constructed by interlayer filling, the image display panel in which the polarizer is laminated on the image display unit is stored in an environment adjusted to the above-mentioned temperature and the above-mentioned relative humidity range for 10 minutes to 3 hours, or After heating at a temperature of 30°C to 90°C, it is bonded to a transparent member such as a front panel.

(Manufacturing method of polarizing element)

The manufacturing method of the polarizing element is not particularly limited, and a typical one is: a method of making a PVA-based resin film previously wound into a roll, stretching, dyeing, crosslinking, etc. (hereinafter referred to as "manufacturing method 1") "); a method including the steps of applying a coating liquid containing a polyvinyl alcohol-based resin on a base film to form a coating layer, and stretching the resulting laminate (hereinafter referred to as "production method 2") .

Production method 1 may include the step of uniaxially stretching the PVA-based resin film, dyeing the PVA-based resin film with a dichroic dye such as iodine to adsorb the dichroic dye, A step of treating the PVA-based resin film on which the dichroic dye is adsorbed is treated with an aqueous solution of boric acid, and a step of washing with water after the treatment with an aqueous solution of boric acid.

The swelling step is a processing step of immersing the PVA-based resin film in a swelling tank. In addition to removing dirt and adhesives on the surface of the PVA-based resin film by the swelling step, uneven dyeing can be suppressed by swelling the PVA-based resin film. A swelling tank generally uses a medium mainly composed of water such as water, distilled water, and pure water. Surfactants, alcohols, etc. can be appropriately added to the swelling tank according to general methods. From the viewpoint of controlling the potassium content of the polarizing element, potassium iodide can be used in the swelling tank. In this case, the concentration of potassium iodide in the swelling tank is preferably 1.5% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass. %the following.

The temperature of the swelling tank is preferably not less than 10°C and not more than 60°C, more preferably not less than 15°C and not more than 45°C, and still more preferably not less than 18°C and not more than 30°C. The immersion time in the swelling tank cannot be generalized because the degree of swelling of the PVA-based resin film is affected by the temperature of the swelling tank. It is more preferably 5 seconds to 300 seconds, more preferably 10 seconds to 200 seconds, and more preferably 20 seconds. More than 100 seconds. The swelling step can be carried out only once, or it can be carried out multiple times as required.

The dyeing step is a treatment step of immersing the PVA resin film in a dye tank, so that the dichroic pigment can be adsorbed and aligned on the PVA resin film. When the dichroic dye is iodine, the dyeing tank is preferably an iodine solution. The iodine solution is generally preferably an iodine aqueous solution, and contains iodine and iodide as a dissolution aid. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide and the like. Among these, potassium iodide is suitable from the viewpoint of controlling the potassium content in the polarizing element.

The concentration of iodine in the dyeing tank (iodine solution) is preferably from 0.01% by mass to 1% by mass, more preferably from 0.02% by mass to 0.5% by mass. The concentration of iodide in the dyeing tank is preferably from 0.01% by mass to 10% by mass, more preferably from 0.05% by mass to 5% by mass, still more preferably from 0.1% by mass to 3% by mass.

The temperature of the dyeing tank is preferably from 10°C to 50°C, more preferably from 15°C to 45°C, still more preferably from 18°C to 30°C. The immersion time in the dyeing tank cannot be generalized because the dyeing degree of the PVA-based resin film is affected by the temperature of the dyeing tank, but it is preferably 10 seconds to 300 seconds, more preferably 20 seconds to 240 seconds. The dyeing step can be performed only once, or multiple times as needed.

The cross-linking step is a treatment step of immersing the PVA-based resin film dyed in the dyeing step in a treatment tank (cross-linking tank) containing a boron compound. By cross-linking the PVA-based resin film with the boron compound, iodine molecules or dye molecules can be adsorbed. in the cross-linked structure. Examples of the boron compound include boric acid, borate, borax and the like. The crosslinking tank is generally an aqueous solution, and may be, for example, a mixed solution of an organic solvent and water that are miscible with water. The crosslinking groove preferably contains potassium iodide from the viewpoint of controlling the potassium content in the polarizing element.

The concentration of the boron compound in the crosslinking tank is preferably from 1% by mass to 15% by mass, more preferably from 1.5% by mass to 10% by mass, still more preferably from 2% by mass to 5% by mass. When potassium iodide is used in the crosslinking tank, the concentration of potassium iodide in the crosslinking tank is preferably from 1% by mass to 15% by mass, more preferably from 1.5% by mass to 10% by mass, still more preferably from 2% by mass to 5% by mass the following.

The temperature of the crosslinking tank is preferably from 20°C to 70°C, more preferably from 30°C to 60°C. The immersion time in the cross-linking tank is affected by the degree of cross-linking of the PVA-based resin film. Although the influence of the temperature of the crosslinking tank cannot be generalized, it is more preferably from 5 seconds to 300 seconds, and more preferably from 10 seconds to 200 seconds. The cross-linking step may be performed only once, or multiple times as required.

The stretching step is a processing step of stretching the PVA-based resin film by a predetermined ratio in at least one direction. Generally, the PVA-based resin film is uniaxially stretched in the conveying direction (longitudinal direction). The stretching method is not particularly limited, and either a wet stretching method or a dry stretching method can be used. The extension step can be implemented only once, or multiple times as needed. The extending step can be performed at any stage in the production of the polarizing element.

A solvent such as water or a mixed solution of an organic solvent and water miscible with water can be generally used in the treatment tank (stretching tank) of the wet stretching method. From the viewpoint of controlling the potassium content in the polarizing element, it is preferable to extend the groove to contain potassium iodide. When potassium iodide is used in the elongation tank, the concentration of potassium iodide in the elongation tank is preferably from 1 mass % to 15 mass %, more preferably from 2 mass % to 10 mass %, still more preferably from 3 mass % to 6 mass % . From the viewpoint of suppressing the cracking of the film during stretching, a boron compound may be contained in the treatment tank (stretching tank). Preferably, it is 1.5 mass % or more and 10 mass % or less, More preferably, it is 2 mass % or more and 5 mass % or less.

The temperature of the elongation tank is preferably from 25°C to 80°C, more preferably from 40°C to 75°C, still more preferably from 50°C to 70°C. The immersion time in the stretching tank cannot be generalized because the degree of stretching of the PVA-based resin film is affected by the temperature of the stretching tank, but it is preferably 10 seconds to 800 seconds, more preferably 30 seconds to 500 seconds. wet extension The elongation treatment of the method can be carried out together with any one or more of the swelling step, the dyeing step, the crosslinking step, and the washing step.

Examples of the dry stretching method include a roller-to-roll stretching method, a heated roller stretching method, a compression stretching method, and the like. Furthermore, in the case of the dry stretching method, the stretching step may be performed together with the drying step.

The total stretching ratio (cumulative stretching ratio) applied to the PVA-based resin film can be appropriately set according to the purpose, and it is preferably 2 times to 7 times, more preferably 3 times to 6.8 times, and more preferably 3.5 times to 6.5 times. times below.

The cleaning step is a treatment step of immersing the PVA-based resin film in a cleaning tank to remove impurities remaining on the surface of the PVA-based resin film. A medium mainly composed of water, such as water, distilled water, or pure water, is used for the washing tank. Furthermore, from the viewpoint of controlling the content of potassium in the polarizing element, it is preferable to use potassium iodide in the cleaning tank. In this case, the concentration of potassium iodide in the cleaning tank is preferably 1% by mass or more and 10% by mass or less, and more preferably 1.5% by mass. % to 4% by mass, more preferably 1.8% to 3.8% by mass.

The temperature of the washing tank is preferably from 5°C to 50°C, more preferably from 10°C to 40°C, still more preferably from 15°C to 30°C. The immersion time in the cleaning tank cannot be generalized because the cleanliness of the PVA-based resin film is affected by the temperature of the cleaning tank, but it is preferably 1 second to 100 seconds, more preferably 2 seconds to 50 seconds, and more preferably 3 seconds More than 20 seconds. The cleaning step may be performed only once, or may be performed multiple times as required.

The drying step is a step of drying the PVA-based resin film washed in the washing step to obtain a polarizing element. Drying can be performed by any suitable method, such as natural drying, air drying, and heating drying.

The production method 2 may include: a step of applying a coating solution containing a PVA-based resin on the base film; a step of uniaxially stretching the obtained laminated film; A step of dyeing the dichroic dye to adsorb the dichroic dye, a step of treating the laminated film having the dichroic dye adsorbed thereon with an aqueous solution of boric acid, and a step of washing with water after the treatment with the aqueous solution of boric acid. In order to form the base film used for a polarizing element, you may use the transparent protective film which is a polarizing plate. The base film can be peeled and removed from the polarizing element as needed.

<Transparent protective film>

The transparent protective film is bonded to at least one side of the polarizing element via the adhesive layer. The transparent protective film can be pasted on one side or both sides of the polarizing element, but it is ideal to stick on both sides.

The transparent protective film may have other optical functions at the same time, and may have a laminated structure in which plural layers are laminated. From the viewpoint of optical properties, the film thickness of the transparent protective film is ideally thin, but if it is too thin, the strength will be low and the workability will be deteriorated. A suitable film thickness is not less than 5 μm and not more than 100 μm, more preferably not less than 10 μm and not more than 80 μm, more preferably not less than 15 μm and not more than 70 μm.

As the transparent protective film, cellulose acyl film, film made of polycarbonate resin, film made of cycloolefin resin such as norcamphene, (meth)acrylic polymer film, polyparaffin film, etc. can be used. Films such as polyester resin films such as diethyl phthalate. When a water-based adhesive such as PVA adhesive is used to attach a transparent protective film to both sides of the polarizer, from the viewpoint of moisture permeability, the transparent protective film on at least one side is preferably a cellulose acyl compound film or (methyl) Any of the acrylic polymer films, particularly preferably a cellulose acylate film.

At least one of the transparent protective films included in the polarizing plate may have a retardation function for the purpose of viewing angle compensation or the like. In this case, the film itself constituting the transparent protective film may have a The retardation function may include a layer without a retardation function and a retardation layer (a layer having a retardation function) in the transparent protective film. When the transparent protective film has a retardation layer, it may be a laminate of a layer without a retardation function and a retardation layer, and these may be bonded using an adhesive or an adhesive.

<Adhesive layer>

As an adhesive agent which comprises the adhesive agent layer for bonding a transparent protective film to a polarizing element, the adhesive agent containing a 1st compound and a 2nd compound is used. As the adhesive, water-based adhesives, solvent-based adhesives, and active energy ray-curable adhesives can be used, but water-based adhesives are more preferable, and PVA-based resins are more preferable. In order to form the adhesive layer, by using the adhesive containing the first compound and the second compound, it is possible to suppress a decrease in the transmittance of the polarizing plate under a high-temperature environment.

The thickness at the time of application of the adhesive agent can be set to an arbitrary value. For example, it is set so that an adhesive layer having a desired thickness can be obtained after curing or heating (drying). The thickness of the adhesive layer is preferably from 0.01 μm to 7 μm, more preferably from 0.01 μm to 5 μm, still more preferably from 0.01 μm to 2 μm, most preferably from 0.01 μm to 1 μm.

When manufacturing a polarizing plate using a polarizer that does not contain the first compound and the second compound, the content of the first compound and the second compound contained in the adhesive is preferably within the range described below. In the case of manufacturing a polarizing plate using a polarizer containing the first compound and the second compound, depending on the first compound and the second compound contained in the polarizer, the content of the first compound and the second compound contained in the adhesive varies from What is necessary is just to change suitably the range demonstrated below. Specific examples of the first compound and the second compound are as described above.

In the case where the adhesive contains a PVA-based resin (for example, in the case of a water-based adhesive containing a PVA-based resin), the content of the first compound is relatively small relative to 100 parts by mass of the PVA-based resin. It is preferably 0.1 to 400 parts by mass, more preferably 1 to 200 parts by mass, still more preferably 3 to 100 parts by mass. When it is less than 0.1 parts by mass, the effect of inhibiting polyalkyleneization of the PVA-based resin in a high-temperature environment may be insufficient. On the other hand, when it exceeds 400 parts by mass, the first compound may precipitate after production of the polarizing plate.

In the case where the adhesive contains a PVA-based resin (for example, in the case of a water-based adhesive containing a PVA-based resin), the content of the second compound is preferably 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the PVA-based resin. Preferably, it is 1.5 to 40 mass parts, More preferably, it is 2 to 35 mass parts. When it is less than 1 part by mass, the effect of suppressing polyalkyleneization of the PVA-based resin in a high-temperature environment may not be sufficient. On the other hand, when it exceeds 50 parts by mass, the second compound may precipitate after production of the polarizing plate.

In the configuration in which a transparent protective film is bonded to both sides of the polarizing element via an adhesive layer, only one side of the adhesive layer of the polarizing element may be a layer containing the first compound and the second compound, However, it is preferable that the adhesive layer on both sides is a layer containing the first compound and the second compound.

In response to the need for thinner polarizers, polarizers with a transparent protective film on only one side of the polarizer have been developed. Even in this configuration, a transparent protective film is laminated via an adhesive agent containing the first compound and the second compound. As a method of manufacturing such a polarizing plate having a transparent protective film on only one side of the polarizing element, a method of peeling off the transparent protective film on one side after first manufacturing a polarizing plate with a transparent protective film on both sides via an adhesive layer is conceivable. . In the case of using such a production method, only one side of the adhesive layer may contain the first compound and the second compound, but it is preferable that both sides of the adhesive layer contain the first compound and the second compound. Yu only When one side of the adhesive layer contains the first compound and the second compound, it is preferable that the adhesive layer on the non-peeling film side contains the first compound and the second compound.

(water-based adhesive)

Any suitable water-based adhesive can be used as the water-based adhesive, and it is ideal to use a water-based adhesive (PVA-based adhesive) containing a PVA-based resin. The average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably from 100 to 5,500, more preferably from 1,000 to 4,500, from the viewpoint of adhesiveness. The average degree of saponification is preferably from 85 mol% to 100 mol% in terms of adhesion, more preferably from 90 mol% to 100 mol%.

As the PVA-based resin contained in the water-based adhesive agent, a PVA-based resin containing an acetoacetyl group (hereinafter referred to as "the PVA-based resin containing an acetoacetyl group") is preferable. The reason for this is that the PVA-based resin layer has good adhesion to the protective film and has good durability. The PVA-based resin containing an acetoacetyl group can be obtained, for example, by reacting a PVA-based resin with diketene by an arbitrary method. A representative example of the degree of modification of the acetoacetyl group of the PVA-based resin containing an acetoacetyl group is 0.1 mol % or more, preferably 0.1 mol % or more and 20 mol % or less. The resin concentration of the water-based adhesive is preferably from 0.1% by mass to 15% by mass, more preferably from 0.5% by mass to 10% by mass.

A crosslinking agent may be contained in the water-based adhesive. A known crosslinking agent can be used as the crosslinking agent. As a crosslinking agent, a water-soluble epoxy compound, a dialdehyde, an isocyanate, etc. are mentioned, for example.

In the case that the PVA-based resin is a PVA-based resin containing an acetoacetyl group, it is preferably any one of glyoxal, glyoxylate, and methylol melamine as a cross-linking agent, preferably glyoxal, glyoxal, Any of the glyoxylates, particularly preferably glyoxal.

The water-based adhesive may contain an organic solvent. From the viewpoint of miscibility with water, alcohols are preferable as organic solvents, and among alcohols, methanol or ethanol is more preferable. The concentration of methanol in the water-based adhesive is preferably from 10% by mass to 70% by mass, more preferably from 15% by mass to 60% by mass, still more preferably from 20% by mass to 60% by mass. When the concentration of methanol is 10% by mass or more, it is possible to more easily suppress polyalkyleneization of the PVA-based resin in a high-temperature environment. And when content of methanol is 70 mass % or less, deterioration of hue can be suppressed. For example, as components to be formulated in water-based adhesives, components having low solubility in water but sufficient solubility in alcohol can be used. In this case, it is also one of the preferable aspects to dissolve the component in alcohol, prepare the alcohol solution of the component, and then add the alcohol solution to the aqueous solution of the PVA-based resin to prepare the adhesive.

(Active energy ray hardening type adhesive)

Active energy ray-curable adhesives are adhesives that are cured by irradiating active energy rays such as ultraviolet rays, such as adhesives containing polymerizable compounds and photopolymerizable initiators, adhesives containing photoreactive resins, adhesives containing adhesives, etc. Adhesives for resins and photoreactive crosslinking agents, etc. Examples of polymerizable compounds include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, photocurable urethane monomers, and oligomers derived from these monomers. . Examples of the photopolymerization initiator include compounds containing substances that generate active species such as neutral radicals, anion radicals, and cationic radicals upon irradiation with active energy rays such as ultraviolet rays.

[Manufacturing method of polarizing plate]

The method of manufacturing a polarizing plate according to this embodiment includes a lamination step of laminating a polarizing element and a transparent protective film. The method of manufacturing a polarizing plate may include a moisture content adjustment step, and the order of performing the lamination step and the moisture content adjustment step is not limited, and the lamination step and the moisture content adjustment step may be performed simultaneously.

In the lamination step, the polarizing element and the transparent protective film are laminated through the above-mentioned adhesive. In the lamination step, an adhesive layer containing the first compound and the second compound is used to bond the polarizer and the transparent protective film. There exists an adhesive agent between a polarizing element and a transparent protective film, and becomes an adhesive agent layer by the process of drying etc., for example. The lamination step may be a step of laminating the polarizer and the transparent protective film using an adhesive that does not contain the first compound and the second compound. In this case, a part of the first compound and a part of the second compound contained in the adhesive may be moved to the polarizing element or the like during the process of forming the adhesive layer from the adhesive.

In the step of adjusting the moisture content, in the case of manufacturing a polarizing plate having the characteristic (a), the moisture content of the polarizing element is adjusted so that the moisture content of the polarizing element becomes equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and a temperature of 20° C. The relative humidity is below the equilibrium moisture content of 80%. The moisture content of the polarizer can be adjusted by the method described above. In the step of adjusting the moisture content, in the case of manufacturing a polarizing plate having the characteristic (b), the moisture content of the polarizing plate is adjusted so that the moisture content of the polarizing plate becomes equal to or higher than the equilibrium moisture content at a temperature of 20° C. and a relative humidity of 30% and a temperature of 20° C. The relative humidity is below the equilibrium moisture content of 80%. The moisture content of the polarizing plate can be adjusted by the method described above.

[Configuration of Image Display Device]

The polarizing plate of this embodiment can be used in various image display devices such as liquid crystal display devices and organic EL display devices. In the case of an image display device, when the two surfaces of the polarizing plate are in contact with a layer other than the air layer, specifically a solid layer such as an adhesive layer, the transmittance tends to decrease in a high-temperature environment. In the image display device using the polarizing plate of this embodiment, even with an interlayer filling configuration, it is possible to suppress a decrease in the transmittance of the polarizing plate in a high-temperature environment.

As a solid layer, an adhesive layer, an adhesive layer, etc. are mentioned, for example. When the solid layer is an adhesive layer, an adhesive layer formed of a UV-curable adhesive is preferable.

The image display device includes, for example, an image display unit, a first adhesive layer laminated on the viewing side surface of the image display unit, and a polarizing plate laminated on the viewing side surface of the first adhesive layer. Such an image display device may further include a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the surface of the second adhesive layer. In particular, the polarizing plate of this embodiment is suitable for use: a transparent member is arranged on the identification side of the image display device, the polarizing plate and the image display unit are bonded by a first adhesive layer, and the polarizing plate and the transparent member are bonded by An image display device with an interlayer filling structure bonded with a second adhesive layer.

The polarizing plate and the image display unit are not limited to the use of the first adhesive layer, and an adhesive layer formed by an adhesive may be used for lamination. The polarizing plate and the transparent member are not limited to the use of the second adhesive layer, and may be bonded using an adhesive layer formed of an adhesive. The adhesive agent described above may be used as the adhesive agent, and the adhesive agent may contain the first compound and the second compound.

<Image display unit>

As an image display unit, for example, a liquid crystal unit, an organic EL cell. As the liquid crystal cell, a reflective liquid crystal cell utilizing external light, a transmissive liquid crystal cell utilizing light from a light source such as a backlight, and a transflective liquid crystal cell utilizing both external light and light from a light source can be used. Any type of liquid crystal unit. When the liquid crystal cell utilizes light from a light source, in the image display device (liquid crystal display device), a polarizing plate is also disposed on the side opposite to the viewing side of the image display cell (liquid crystal cell), and the light source is disposed. It is ideal that the polarizing plate on the light source side and the liquid crystal cell are bonded through a suitable adhesive layer. As the driving method of the liquid crystal unit, such as VA (Vertical Alignment, vertical alignment) mode, IPS (In-Plane Switching, plane switching) mode, TN (Twisted Nematic, twisted nematic) mode, STN (Super-Twisted Nematic, super Arbitrary modes such as twisted nematic) mode and bend alignment (π-type).

As an organic EL cell, those in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a luminous body (organic electroluminescence luminous body) are suitably used. The organic light-emitting layer is a laminate of various organic thin films. For example, a laminate of a hole injection layer made of triphenylamine derivatives and a light-emitting layer made of fluorescent organic solids such as anthracene can be used; these A laminate of a light-emitting layer and an electron injection layer made of a perylene derivative or the like; or a hole injection layer, a laminate of a light-emitting layer and an electron injection layer, etc., constitutes various layers.

<Adhesion of image display unit and polarizing plate>

The bonding of the image display unit and the polarizing plate is preferably performed using the first adhesive layer. Among them, the method of bonding the polarizing plate with the adhesive layer attached with the first adhesive layer on one side of the polarizing plate to the image display unit is preferable from the viewpoint of workability and the like. Attaching the first adhesive layer to the polarizing plate can be performed in an appropriate manner. As an example, for example, the matrix polymer or its composition is dissolved or dispersed in a solvent composed of a simple substance or a mixture of suitable solvents such as toluene and ethyl acetate, and the amount is adjusted to 10% by mass to 40% by mass. Adhesive solution of the following left or right is directly attached to the polarizing plate by a suitable unfolding method such as casting method or coating method; the first adhesive layer is formed on the release film, and it is transferred to the polarizing plate. way etc.

<1st adhesive layer, 2nd adhesive layer>

The first adhesive layer and the second adhesive layer (either or both are referred to as "adhesive layer" below) independently may be composed of one layer or two or more layers, preferably one layer. The adhesive layer can be composed of an adhesive composition mainly composed of (meth)acrylic resin, rubber resin, urethane resin, ester resin, silicone resin, and polyvinyl ether resin. Among them, an adhesive composition comprising a (meth)acrylic resin excellent in transparency, weather resistance, heat resistance, etc. as a matrix polymer is suitable. The adhesive composition may be an active energy ray curing type or a thermosetting type.

As the (meth)acrylic resin used for the adhesive composition, for example, butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylic acid A polymer or copolymer in which one or more of (meth)acrylates such as 2-ethylhexyl ester are monomers. In the matrix polymer, it is ideal to copolymerize with polar monomers. Examples of polar monomers include (meth)acrylic acid compounds, 2-hydroxypropyl (meth)acrylate compounds, hydroxyethyl (meth)acrylate compounds, (meth)acrylamide compounds, (meth)acrylic acid N , A monomer having a carboxyl group, a hydroxyl group, an amido group, an amino group, an epoxy group, etc., such as an N-dimethylaminoethyl ester compound and a glycidyl (meth)acrylate compound.

The adhesive composition may only contain the above-mentioned matrix polymer, and usually further contains a cross-linking agent. As a crosslinking agent, for example, a metal ion having a divalent or higher valence and forming a metal carboxylate salt with a carboxyl group, a polyamine compound forming an amide bond with a carboxyl group, and a polyamine compound forming an ester bond with a carboxyl group. Epoxy compounds or polyalcohols, polyisocyanate compounds that form amide bonds with carboxyl groups. Among them, polyisocyanate compounds are more preferable.

The active energy ray-curable adhesive composition has the property of being hardened by irradiation of active energy rays such as ultraviolet rays and electron rays, and has adhesiveness before irradiation of active energy rays, and can be adhered to an adherend such as a film. Hardened by irradiation of active energy rays, it has the property of adjusting the adhesive force. The active energy ray-curable adhesive composition is preferably an ultraviolet-curable adhesive composition. The active energy ray curable adhesive composition may further contain an active energy ray polymerizable compound in addition to the matrix polymer and the crosslinking agent. A photopolymerization initiator, a photosensitizer, etc. may be contained as needed.

The adhesive composition may contain fine particles for imparting light scattering, beads (resin beads, glass beads, etc.), glass fibers, resins other than matrix polymers, adhesiveness imparting agents, fillers, etc. Additives for fillers (metal powders, other inorganic powders, etc.), antioxidants, ultraviolet absorbers, dyes, pigments, colorants, defoamers, anti-corrosion agents, photopolymerization initiators, etc.

The adhesive layer can be formed by applying an organic solvent dilution of the above-mentioned adhesive composition on the surface of a substrate film, an image display unit, or a polarizing plate, and drying it. The base film is generally a thermoplastic resin film, and a typical example thereof is a release film subjected to a release treatment. The release film, for example, is made of polysilicon on the surface of the film made of resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, etc. where the adhesive layer is formed. Release treatment such as oxygen treatment.

The adhesive composition can be directly coated on the release-treated surface of the release film to form an adhesive layer, and the adhesive layer with the release film can be laminated on the surface of the polarizing plate. It is also possible to directly coat the adhesive composition on the surface of the polarizing plate to form an adhesive layer, and layer a release film on the outer surface of the adhesive layer.

When an adhesive layer is provided on the surface of the polarizing plate, it is ideal to perform surface activation treatment such as plasma treatment and corona treatment on the bonding surface of the polarizing plate and/or the bonding surface of the adhesive layer, so as to implement electric Halo processing is more ideal.

Furthermore, an adhesive composition is coated on a second release film to form an adhesive layer, a release film is laminated on the formed adhesive layer, an adhesive sheet is prepared, and the second release film is peeled off from the adhesive sheet. The final adhesive layer with release film can be laminated on the polarizing plate. As the second release film, the adhesive force with the adhesive layer is weaker than that of the release film and it is easy to peel off.

The thickness of the adhesive layer is not particularly limited, for example, it is preferably 1 μm to 100 μm, more preferably 3 μm to 50 μm, and may be 20 μm or more.

<transparent member>

As a transparent member arranged on the viewing side of the image display device, for example, a transparent plate (front panel, window layer), a touch panel, or the like. As the transparent plate, a transparent plate having suitable mechanical strength and thickness can be used. Such a transparent plate includes, for example, a polyimide-based resin, acrylic resin, polycarbonate-based transparent resin plate, a glass plate, or the like. Functional layers such as an antireflection layer may also be laminated on the viewing side of the transparent plate. Furthermore, when the transparent plate is a transparent resin plate, a hard coat layer for improving physical strength or a low moisture permeability layer for reducing moisture permeability may be laminated. As the touch panel, various touch panels such as a resistive film type, a capacitive type, an optical type, and an ultrasonic type, a glass plate having a touch sensing function, a transparent resin plate, and the like can be used. When using a capacitive touch panel as a transparent member, it is preferable to provide a transparent plate made of glass or a transparent resin plate on the viewing side of the touch panel.

<Adhesion of polarizing plate and transparent member>

When laminating the polarizing plate and the transparent member, an adhesive or an active energy ray-curable adhesive is suitably used. In the case of using an adhesive, the attachment of the adhesive can be performed in a suitable manner. As a specific method of attaching the adhesive, for example, the aforementioned method of attaching the adhesive used for laminating the image display unit and the polarizing plate.

In the case of using an active energy ray hardening type adhesive, in order to prevent the diffusion of the adhesive solution before hardening, it is suitable to use a dam that surrounds the periphery of the image display panel, place a transparent member on the dam and The method of injecting the adhesive solution. After injecting the adhesive solution, alignment and defoaming are carried out as necessary, and curing is performed by irradiating active energy rays.

[Example]

Hereinafter, the present invention will be specifically described based on examples. Materials, reagents, amounts of substances, ratios thereof, operations, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the present invention is not limited to the following examples.

<Production of Polarizer A>

A PVA-based resin film with a thickness of 40 μm, which is composed of a PVA-based resin with an average degree of polymerization of about 2400 and a saponification degree of 99.9 mol% or more, is uniaxially stretched about 5 times in a dry method, and immersed in a stretched state. After 1 minute of pure water at 60° C., it was immersed in an aqueous solution at a temperature of 28° C. at a weight ratio of iodine/potassium iodide/water of 0.05/5/100 for 60 seconds. Then, it was immersed in the aqueous solution of temperature 72 degreeC whose weight ratio of potassium iodide/boric acid/water was 8.5/8.5/100 for 30 seconds. Next, it was washed with pure water at a temperature of 26° C. for 20 seconds, and then dried at a temperature of 65° C. to obtain a polarizer A with a thickness of 15 μm in which iodine was adsorbed and aligned to the PVA-based resin layer. The thickness of the polarizing element A was measured using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

<Preparation of Adhesives 1 to 5>

(Preparation of PVA solution A for adhesive)

50 g of an acetoacetyl group-containing modified PVA-based resin ("GOHSENEX Z-410" manufactured by Mitsubishi Chemical Corporation) as a PVA-based resin was dissolved in 950 g of pure water. This solution was heated at a temperature of 90° C. for 2 hours and then cooled to normal temperature to obtain a PVA solution A for an adhesive agent.

(Preparation of Adhesives 1 to 5)

The concentration of the PVA-based resin was 3.0% by mass, and the contents of the first compound and the second compound were shown in Table 1. PVA solution A, the first compound, the second compound, and pure water were prepared to prepare adhesives 1 to 5. As the first compound, 4-hydroxy-2,2,6,6-tetramethyl-1-oxypiperidine (hereinafter also referred to as "TEMPOL") was used.

[Table 1]

<Preparation of transparent protective film A>

After immersing a commercially available cellulose acylate film ("TD40" manufactured by Fuji Film Co., Ltd., thickness 40 μm) in a 1.5 mol/liter NaOH aqueous solution (saponified solution) kept at 55°C for 2 minutes, the cellulose acylate was washed with water. membrane. Then, after immersing in a 0.05 mol/L sulfuric acid aqueous solution at a temperature of 25° C. for 30 seconds, it was passed through running water in a washing tank for 30 seconds to bring the cellulose acylate film into a neutral state. Then, the air knife was used to remove the water repeatedly 3 times to remove the moisture, and left in an oven at a temperature of 70° C. for 15 seconds to dry to prepare a saponified cellulose acyl film as a transparent protective film A.

<Production of Polarizing Plate 1>

The transparent protective film A was laminated on both sides of the polarizing element A using the adhesive 1 using a roller laminating machine, and dried at a temperature of 80° C. for 5 minutes to form an adhesive layer and obtain a polarizing plate 1 . The usage-amount of the adhesive agent 1 was adjusted so that the thickness of both sides of the adhesive agent layer after drying might become 50 nm.

<Production of Polarizing Plates 2 to 5>

Polarizing plates 2 to 5 were obtained in the same manner as the production of the polarizing plate 1 described above except that the adhesive 1 was changed to the adhesives 2 to 5 .

(Adjustment of moisture content of polarizing plate (polarizing element))

The polarizing plates 1 to 5 obtained above were preserved for 72 hours under the conditions of a temperature of 20° C. and a relative humidity of 40%. The water content after 66 hours, 69 hours, and 72 hours from the storage under the above conditions was measured by Karl Fischer. Since the values of the respective moisture contents obtained by the measurement do not change, the moisture contents of the polarizing plates 1 to 5 can be considered to be the same as the equilibrium moisture contents of the 72-hour storage environment. When the moisture content of the polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing element in the polarizing plate can also be considered to be in equilibrium with the storage environment. Moreover, when the moisture content of the polarizing element in the polarizing plate reaches equilibrium in a certain storage environment, the moisture content of the polarizing plate can also be considered to be in equilibrium with the storage environment.

<Evaluation of high temperature durability>

(Preparation of samples for evaluation)

An adhesive layer was formed using an acrylic adhesive (manufactured by Lintec, product number: #7) on both surfaces of the polarizing plates 1 to 5 after adjusting the moisture content. The absorption axis of polarizing plates 1 to 5 was parallel to the long side, and cut into a size of 50mm×100mm, and an alkali-free glass ("EAGLE XG" manufactured by Corning Incorporated]) was attached to the surface of each adhesive layer to prepare samples for evaluation.

(Evaluation of change in penetration rate due to high temperature durability test (105°C))

The samples for evaluation were subjected to autoclave treatment at a temperature of 50°C and a pressure of 5 kgf/cm ² (490.3 kPa) for 1 hour, and then left to stand in an environment of a temperature of 23°C and a relative humidity of 55% for 24 hours. Measure the luminance of the sample for evaluation at this time, using a spectroradiometer ("SR-UL1R" manufactured by Topcon Techno House Co., Ltd.), place the sample for evaluation on the irradiation surface of the backlight module with a luminance of 5000cd/cm ² , and measure it at an angle of Measured under the conditions of 2 degrees and a measuring distance of 350mm. The luminance measured under this condition is "luminance L0". Then, the samples for evaluation were stored in a heating environment at 105°C for a storage time of 72 to 240 hours, and the samples for evaluation were measured every 24 hours in the same procedure as above. The measured luminance was taken as "luminance L1" of the luminance after the high-temperature durability test.

Using the measured luminance L0 and luminance L1, the amount of change in transmittance was calculated according to the following formula.

Transmittance change [%]=100-(brightness L1/brightness L0)×100

Based on the storage time under the above-mentioned heating environment required to obtain the luminance L1 when the change amount of the transmittance is 5% or more, the high-temperature durability was evaluated using the following evaluation criteria. The results are shown in Table 2.

(evaluation criteria)

The storage time of the evaluation sample under the heating environment required when the change in the transmittance of the evaluation sample is 5% or more is

More than 240 hours: A

More than 120 hours to 240 hours: B

More than 72 hours to 120 hours: C

Until 72 hours: D

[Table 2]

Claims (12)

A polarizing plate comprising a polarizing element in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol-based resin layer, and a transparent protective film laminated on at least one side of the polarizing element; Wherein, the above-mentioned polarizing element and the above-mentioned transparent protective film are bonded by an adhesive layer formed by an adhesive containing the first compound and the second compound; The aforementioned first compound is a compound having a nitroxide free radical or a nitrogen oxide group; The aforementioned second compound is cyclodextrins. The polarizing plate according to claim 1, wherein the first compound is an N-oxyl compound. The polarizing plate according to claim 1 or 2, wherein the second compound is at least one selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin. The polarizing plate according to any one of claims 1 to 3, wherein the adhesive contains a polyvinyl alcohol-based resin. The polarizing plate according to claim 4, wherein, in the adhesive, the content of the first compound is not less than 0.1 parts by mass and not more than 400 parts by mass relative to 100 parts by mass of the polyvinyl alcohol-based resin. The polarizing plate according to claim 4 or 5, wherein, in the adhesive, the content of the second compound is not less than 1 part by mass and not more than 50 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol-based resin. The polarizing plate according to any one of claims 1 to 6, wherein the adhesive layer has a thickness of 0.01 μm or more and 7 μm or less. The polarizing plate according to any one of claims 1 to 7, wherein the aforementioned polarizing plate is used in an image display device; In the image display device, it is provided so that both surfaces of the polarizing plate are in contact with the solid layer. An image display device comprising: an image display unit; a first adhesive layer laminated on the identification side surface of the image display unit; and claim 18 laminated on the identification side surface of the first adhesive layer The polarizing plate described in any one of the above. The image display device according to claim 9, further comprising: a second adhesive layer laminated on the viewing side surface of the polarizing plate, and a transparent member laminated on the viewing side surface of the second adhesive layer. The image display device according to claim 10, wherein the transparent member is a glass plate or a transparent resin plate. The image display device according to claim 10, wherein the transparent member is a touch panel.